What is the appropriate course of action for a previously healthy adult experiencing numbness in their fingers and feet?

Numbness in Fingers and Feet: Clinical Approach

Begin with fasting blood glucose and HbA1c testing immediately, as diabetes is the most common treatable cause of peripheral neuropathy presenting with distal numbness. 1, 2

Initial Diagnostic Workup

Order the following laboratory tests first:

• Fasting blood glucose and HbA1c (diabetes screening) 1, 2
• Complete blood count (anemia, infection, malignancy) 1, 2
• Vitamin B12 level (especially if patient takes metformin ≥2g daily) 1, 2
• Thyroid function tests (TSH, free T4) 2
• Hepatitis C serology if risk factors present 1

Conduct a focused medication review looking specifically for metformin (especially ≥2g daily), chemotherapy agents, and statins as common culprits causing neuropathy. 1

Physical Examination Priorities

Assess fiber type involvement to guide diagnosis:

• Small fiber testing: Ask about burning pain and tingling; test pinprick sensation and temperature perception 3, 1, 4
• Large fiber testing: Ask about numbness with loss of balance; perform vibration perception with 128-Hz tuning fork and 10-g monofilament testing 3, 1, 4

Determine distribution pattern:

• Distal symmetric (stocking-glove) distribution suggests metabolic or toxic causes like diabetes 1
• Patchy or asymmetric distribution suggests mononeuropathy multiplex from vasculitis 1
• Bilateral hands with unilateral leg involvement raises concern for multiple compression neuropathies or CIDP 2

Check for red flags requiring urgent evaluation:

• Hemibody sensory loss without motor weakness requires stroke evaluation within 48 hours 1, 2

Treatment Algorithm

If Diabetes is Identified:

Optimize glycemic control aggressively (HbA1c target 6-7%)—this is the only proven strategy to prevent or delay diabetic neuropathy progression. 3, 1, 4 Note that glycemic control does not reverse existing neuronal loss. 3, 4

For Symptomatic Management:

First-line pharmacologic options (choose one):

• Duloxetine 3, 1, 4
• Pregabalin 3, 1, 5
• Gabapentin 3, 1

If first-line agents fail, consider:

• Tricyclic antidepressants (amitriptyline) 1
• Topical capsaicin (8% patch or 0.075% cream) 1

Non-Pharmacologic Interventions:

Recommend physical activity for all patients with neuropathy—this benefits both diabetic and chemotherapy-induced neuropathy. 3, 1, 4

Offer acupuncture for musculoskeletal-related neuropathic symptoms. 3, 1

If Vitamin B12 Deficiency:

Supplement with 2500 mcg daily, particularly in metformin users. 1

Critical Pitfalls to Avoid

Do NOT use acetyl-L-carnitine for prevention of chemotherapy-induced peripheral neuropathy—harms outweigh benefits. 1

Avoid opioids (tapentadol, tramadol) for chronic neuropathic pain due to addiction risk. 1

Monitor metformin users closely for B12 deficiency, as long-term use causes neuropathy in a stocking-glove distribution. 1

Start medications at lower doses in older patients and titrate slowly to minimize adverse events. 1

Ongoing Monitoring

Perform annual foot examinations with 10-g monofilament testing once loss of protective sensation is documented to prevent ulceration and amputation. 3, 1

Assess for autonomic signs including orthostatic hypotension, resting tachycardia, and skin dryness/cracking. 1

When to Refer

Refer to neurology if:

• Electrodiagnostic studies are needed 2
• Diagnosis remains unclear after initial workup 2
• Asymmetric distribution suggests mononeuropathy multiplex 1

Refer to endocrinology if newly diagnosed or poorly controlled diabetes is identified. 2

Consider vascular surgery referral if absent lower extremity pulses or vascular bruits are present. 3, 2